Numerical Ability
Divisibility by 11 — Alternating sum of digits must be 0 or divisible by 11. Example: 121 → 1−2+1=0, divisible. Quick check for large numbers in data interpretation.
BODMAS Left-to-Right Trap — Division and Multiplication have equal priority (left-to-right), as do Addition and Subtraction. 20÷5×2 = (20÷5)×2 = 8, NOT 20÷10=2.
Percentage-Fraction Quick Converts — 12.5%=1/8, 16.67%=1/6, 33.33%=1/3, 62.5%=5/8, 87.5%=7/8. Memorize these; they speed profit-loss and discount problems enormously.
Alligation Shortcut — For mixture problems: draw a cross, write mean in center, cheaper/dearer at ends. Ratio = (Dearer−Mean):(Mean−Cheaper). Instant solution without equations.
Compound Interest ≈ SI + (SI²/200P) — For 2 years, CI approximately equals Simple Interest plus (SI squared divided by 200 times Principal). Useful when options are far apart.
LCM×HCF = Product of Two Numbers — If two numbers given and one measure asked, use this identity instantly. Example: LCM=60, one number=12 → other = 60×HCF/12.
Speed-Distance: Relative Speed — Same direction: subtract speeds; opposite direction: add speeds. Trains crossing, boats upstream/downstream—master this for 2-3 guaranteed marks.
Digit Sum for 3 and 9 — Number divisible by 3 (or 9) iff digit-sum divisible by 3 (or 9). Eliminates options in series, simplification, and number-system MCQs within seconds.
Mensuration: Circle in Square Waste — When circle inscribed in square of side *a*, wasted area = a²(1 − π/4) ≈ 0.215a². Memorize 21.5% waste for instant MCQ elimination.
Time-Work: M₁D₁H₁/W₁ = M₂D₂H₂/W₂ — MDH formula (Men×Days×Hours per Work) solves all variations. If men double and days halve, work remains same. One formula, all time-work problems.
Average: New Average Shift — When one element added, new average = old average ± (difference from old avg)/(n+1). Saves recalculation in data-interpretation tables.
Geometry: Angle-Sum Polygon — Sum of interior angles = (n−2)×180°. For hexagon: 4×180°=720°. Each exterior angle of regular polygon = 360°/n. Two formulas, all polygon MCQs covered.
Logical Reasoning and Mental Ability
Blood Relations: SAMDHI Code — Sister/Son = self generation; Aunt/Uncle = parent generation; Mother/Father = +1 generation; Daughter = −1 generation; Husband/Wife = spouse (same gen). Decode any complex chain.
Direction Sense: NEWS Clockwise — North→East→South→West rotates clockwise; right-turn goes next letter, left-turn goes previous. Starting North, two rights = East. Instant orientation fixes.
Coding-Decoding: +N Pattern — If CAT=DBU (each letter +1), check consistent shift across alphabet. A=1, B=2... Z=26 reverse coding (A=26) also common. Spot the rule in 10 seconds.